Hitherto, such a kind of air-conditioner controls a room temperature by a fuzzy control as shown in FIG. 4. For example, the air-conditioner comprises: a fuzzy control memory section 1 having control rules, for example, as shown in the following mathematical expressions 1(a) to 1(f) and membership functions shown in FIGS. 5 to 7; and a control apparatus 3 for controlling a switching amount of an operating frequency of a compressor 2 in accordance with the results of the fuzzy arithmetic operations using the above control rules and membership functions. A temperature difference between a room temperature (Tr) and a set temperature (Ts) is set to an input 1, a change amount of the room temperature is set to an input 2, and a degree at which the inputs 1 and 2 satisfy the control rule is calculated with reference to membership functions (A) (fuzzy arithmetic operations are executed).
______________________________________ Mathematical expressions 1 ______________________________________ (a) if E = NB and D = NB then F = PB (b) if E = NB and D = PB then F = ZR (c) if E = ZR and D = NB then F = PB (d) if E = ZR and D = ZR then F = ZR (e) if E = PB and D = PB then F = NB (f) if E = PB and D = NB then F = ZR ______________________________________
where,
E: temperature difference between the room temperature (Tr) and the set temperature (Ts) PA1 D: time-dependent change ((Tr1-Tr2)/min) PA1 F: switching amount of the operating frequency of the compressor
In the above mathematical expressions 1(a) to 1(f), the input variable E of the antecedent part of the control rule is set to (Tr-Ts), the input variable D is set to a change amount of the room temperature (for example, (Tr1-Tr2)/min), the output variable F of the consequent part is set to a change amount off the operating frequency off the compressor, D denotes a change amount of the room temperature, E indicates a temperature difference (Tr-Ts), and F shows a switching amount of the operating frequency of the compressor. In the above mathematical expressions and a diagrams of the membership functions (A) shown in FIGS. 8 and 9, a value of NB largely changes toward the negative direction, a value of ZR is equal to 0 (no change), and a value of PB largely changes toward the positive direction.
The control rules of the above mathematical expressions and the membership functions shown in FIGS. 5 to 7 are determined as shown in intermediate characteristics for both of the stability of the room temperature and the response speed to a rapid change in the room due to a disturbance (opening or closure of the door or window). The control apparatus 3 controls a fan in the room, an outdoor fan, and the like on the basis of the room temperature, set temperature, and the like.
The above fuzzy arithmetic operations are executed at every predetermined interval (t seconds) during the operation of the air-conditioner. The switching amount of the operating frequency of the compressor 2 is controlled on the basis of the results of the fuzzy arithmetic operations. The above predetermined interval (t seconds) has been preset to an optimum value on the basis of the results of experiments according to the actual state of the air-conditioner. For example, the above predetermined interval is set to a value which is not too long or too short.
That is, this is because as: shown in. FIG. 8 when the predetermined interval is set to a long value t.sub.1 (&gt;t), the switching speed of the operating frequency of the compressor 2 for a fluctuation of the room temperature (Tr) is slow and the stability of the room temperature remarkably deteriorates and comfortableness is eventually deteriorated. On the contrary, this is because as shown in FIG. 9, when the predetermined interval is set to a short value t.sub.2 (&lt;t), the switching speed of the operating frequency of the compressor 2 for the fluctuation of the room temperature (T.sub.r) is fast and the stability of the room temperature is very good, but since the operating frequency is frequently switched, in the case where the operation is continued for a long time, an electric power consumption of the air-conditioner is large and the operating efficiency eventually deteriorates.
At present, the predetermined interval (t seconds) is set to an intermediate value between the above values t.sub.1 and t.sub.2.
In the above control apparatus of the air-conditioner, however, in the case where the room temperature (Tr) rapidly changes by a disturbance or the like as shown in FIG. 10, for example, in the case where the window is temporarily opened during the warming operation and the room temperature suddenly drops (the case where the room temperature drops from A time point to B time point in FIG. 10), the operating frequency of the compressor 2 is switched only at every predetermined interval (t seconds) mentioned above. Therefore, a response speed is slow, namely, a leading speed of the room temperature is slow, it takes a time until the room temperature is returned to a comfortable value, and the comfortableness is consequently lost.